In two way communication systems such as those described in U.S. Pat. No. 4,875,038 filed Jan. 7, 1988 by Siwiak et al., entitled "Frequency Division Multiplexed Acknowledge Back Paging System," hereinafter referred to as Siwiak '038, it is desirable to provide a pager radio user with several possible responses from which one response is selected to be transmitted back to the paging fixed network, where it is sent to the caller who initiated the call. One method of providing such responses in a pager is described in U.S. Pat. No. 5,153,582 filed Aug. 7, 1989 by Davis, entitled "Method and Apparatus for Acknowledging and Answering a Paging Signal," hereinafter referred to as Davis '582.
In an analog communication system such as that described in application Ser. No. 08/395,747 filed Feb. 28, 1995 by Leitch et al., entitled "Voice Compression Method and Apparatus in a Communication System", which is hereby incorporated by reference, and referred to hereinafter as Leitch '747, voice messages are compressed by techniques described therein, and then transmitted on a radio channel or a subchannel of radio channel, using a synchronous protocol, such as the well known InFLEXion.TM. protocol, licensed by Motorola, Inc. of Shaumburg, Ill.
In a system using such an analog protocol for signals sent from the paging fixed network to the pager, as described in Leitch '747, and having acknowledge capability, as described in Siwiak '038 and Davis '582, it is also desirable to be able to include, in a message that has an information part, a plurality of probable analog responses pertaining thereto, thus avoiding the problem of having either no responses available, or only a rigidly defined set of responses which have been predetermined for use by each pager user, and which may not turn out to pertain to an information part of a particular message. When such probable responses are included within the message received by the pager, they can then be stored in the pager. The user can review the responses, select one, and transmit the response, or an identifier corresponding to that response back to the paging fixed network for delivery to the caller.
A first issue in such a system is how to separate the plurality of probable analog responses carried within the message. One method which can be used is to utilize the predetermined synchronous protocol divisions for identifying the locations of the analog parts. This method would work but has a significant deficiency. The deficiency is determining where the analog responses are located within the synchronous protocol and what their duration is. While this problem can be solved digitally by using pointers and digital duration information, it is fairly complex to have the controller handle the digital position determination while also decompressing and decoding the analog information.
Another issue which arises in a pager having voice response capabilities is how to provide for user selection of one of the voice responses. In an alphanumeric pager such as described in Davis '582, the problem is solved by dedicating several keys for response selection. When there are at least a moderate (say, 8 to 12) number of keys, dedicating several for response selection works well. However, in simple analog pagers, in which there may be only a very few keys (i.e., less than 8, and perhaps as few as 2), a problem arises as to how a selection of a voice response is conveniently made.
What is needed is a technique for identifying a plurality of analog responses included in an analog message, which is efficient in terms of the required complexity of decoding and channel time used.